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A titration of sodium hydroxide solution with hydrochloric acid can be carried out as follows: 1 - Edexcel - GCSE Chemistry - Question 2 - 2018 - Paper 1
Question 2
A titration of sodium hydroxide solution with hydrochloric acid can be carried out as follows: 1. A pipette is used to measure 25.00 cm³ of sodium hydroxide solutio... show full transcript
Worked Solution & Example Answer:A titration of sodium hydroxide solution with hydrochloric acid can be carried out as follows: 1 - Edexcel - GCSE Chemistry - Question 2 - 2018 - Paper 1
Step 1
Describe how the pipette should be used to measure exactly 25.00 cm³ of sodium hydroxide solution into the conical flask.
Answer
To accurately measure 25.00 cm³ of sodium hydroxide solution with a pipette, follow these steps:
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Use a pipette filler: Begin by using a pipette filler to draw the sodium hydroxide solution into the pipette. This prevents contamination and minimizes the risk of spillage.
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Wash the pipette: Ensure that the pipette has been washed with sodium hydroxide solution beforehand to avoid any contamination that could affect the measurement.
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Fill the pipette: Draw the liquid up into the pipette until it exceeds the 25.00 cm³ mark.
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Adjust the level: Place the pipette vertically and release the liquid until the bottom of the meniscus (the curved surface of the liquid) touches the 25.00 cm³ line. This ensures an accurate measurement.
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Transfer to the conical flask: Finally, release the liquid from the pipette into the conical flask, making sure to let out all of the solution from the pipette.
Step 2
Explain why the burette is rinsed with the acid.
Answer
Rinsing the burette with the hydrochloric acid before filling it with the solution serves two important purposes:
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Avoid contamination: Rinsing removes any residual water or contaminants in the burette that could dilute the acid solution, ensuring that the concentration of hydrochloric acid remains consistent throughout the titration.
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Maintain accuracy: If the burette were not rinsed with acid, any leftover water could interfere with the addition of acid to the sodium hydroxide solution. This would lead to an inaccurate volume being delivered, affecting the results of the titration and making it difficult to determine the endpoint accurately.